The 2004 Scottish grouse season could be the worst for a decade as bad weather and disease hit stocks.
Bad weather and disease have hit grouse stocks
The Game Conservancy Trust said many events planned for the "Glorious Twelfth" - the first day of the shooting season - had been cancelled.
Grouse stocks are prone to fluctuation but it is believed global warming has added to the problems.
Insects which chicks depend on are appearing too early, while beetles have attacked their other food, heather.
Some adult birds have been affected by the gut parasite, trichostrongylus tenius, which has hindered them while raising their chicks.
The trust said that warm conditions earlier in the year were encouraging but there had been "unremittingly damp weather throughout late spring and summer".
Its weather station in Strathspey recorded only five dry days in June, temperatures have been well below average and areas of the Cairngorms saw snow down to 2,000ft for several days in mid-June.
It is thought that such weather conditions caused the disappearance of many of the large broods of small "bumble-bee" sized chicks sighted in early June after hatching time.
On top of those factors, the trust has continued to receive reports of rising numbers of sheep ticks. Blood sucking by the parasites can reduce grouse chick growth rates.
Adam Smith, the trust's senior uplands scientist in Scotland, said: "There is a pattern of poor grouse breeding success this year and we have identified a number of possible causes.
"A common theme could be hen grouse coming into the spring breeding season in poor condition.
"This may reflect last year's severe drought and winter frost damage which probably affected heather quality coupled with last and this year's damaging outbreaks of heather beetle.
"By and large this season is probably going to see the fewest number of days
grouse shooting in Scotland for maybe eight to 10 years."
Grouse hunting can normally expect to bring £15m-£20m into the Scottish economy in an average year.
But the Moorland Association said that despite the dire forecast there would be some good shoots around.
Simon Bostock, the association's chairman, added: "Strong populations are very good news for moor owners and the local economy that relies on income from shooting customers.
"No matter how good your keepering may be, each year's weather is a huge factor in a grouse moor's success."